The invention relates to an apparatus for the transmission of ultrasonic energy of a predetermined wavelength to a liquid, which apparatus includes a rod or tube-like resonator of a length which is 1/2 the wavelength of the ultrasound or a multiple thereof and an ultrasonic generator which is adapted to generate longitudinal vibrations and which is coupled to the face of the resonator.
Such apparatus are utilized especially in ultrasonic cleaning equipment. In this equipment the ultrasonic generator is mounted on the wall of a liquid container with the resonator (radiating member) extending into the liquid in the container.
The longitudinal vibrations transmitted to the resonator from the generator coupled thereto are partially converted to transversal vibrations so that ultrasonic energy is emitted from the resonator in axial as well as in radial direction with respect to the resonator axis. Generally, however, only the radially emitted ultrasonic radiation is desirable; the longitudinally emitted radiation, that is, the radiation emitted from the face of the resonator, can usually not be utilized. In order to convert the longitudinal vibration as supplied to the resonator to a large degree into vibration emitted radially from the resonator, it has been proposed (U.S. Pat. No. 4,537,511) to mount the resonator to the face of the ultrasonic generator at a point with a longitudinal vibration maximum and to tune the length of the resonator to an integral multiple of 1/2 the wavelength (lambda/2) of the longitudinal vibration supplied to the resonator by the ultrasonic generator. By coupling the resonator to the generator at a point of maximum vibration thereof the full energy output of the generator is transmitted to the resonator thereby providing for maximal radiation results particularly with its length tuned to the frequency of the ultrasonic generator. However, even with this known arrangement there are the undesirable losses as a result of longitudinally emitted vibration.
It is the object of the present invention to provide an apparatus which eliminates to a large degree the longitudinally emitted vibration and the resulting losses, that is, a transducer in which the longitudinal vibration supplied to the resonator by the ultrasonic generator is effectively fully transformed into transverse radial radiation.